EP0154861B1 - Reflection mirror - Google Patents
Reflection mirror Download PDFInfo
- Publication number
- EP0154861B1 EP0154861B1 EP85101928A EP85101928A EP0154861B1 EP 0154861 B1 EP0154861 B1 EP 0154861B1 EP 85101928 A EP85101928 A EP 85101928A EP 85101928 A EP85101928 A EP 85101928A EP 0154861 B1 EP0154861 B1 EP 0154861B1
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- EP
- European Patent Office
- Prior art keywords
- liquid crystal
- crystal cell
- reflection mirror
- film
- thin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/133553—Reflecting elements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
- B60R1/00—Optical viewing arrangements; Real-time viewing arrangements for drivers or passengers using optical image capturing systems, e.g. cameras or video systems specially adapted for use in or on vehicles
- B60R1/02—Rear-view mirror arrangements
- B60R1/08—Rear-view mirror arrangements involving special optical features, e.g. avoiding blind spots, e.g. convex mirrors; Side-by-side associations of rear-view and other mirrors
- B60R1/083—Anti-glare mirrors, e.g. "day-night" mirrors
- B60R1/088—Anti-glare mirrors, e.g. "day-night" mirrors using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors
Definitions
- the invention relates to a controllable reflection mirror according to the preamble of claim 1.
- US-A-3,862,798 discloses a rear view mirror assembly comprising a reflective surface, and a liquid crystal assembly covering the reflective surface.
- the liquid crystal assembly comprises a thin layer of liquid nematic material sandwiched between rigid panes of transparent material, the rigid panes having a thin, transparent coating of conductive material thereon in uniform contact with the nematic material.
- the controlled output of a voltage source is applied to the coatings of conductive material so that transmittivity of light by the nematic material is changed.
- DE-A-2,653,818 discloses a liquid crystal cell comprising a glass substrate for changing transmittivity of light incident thereto in accordance with an electric voltage applied thereto.
- the glass substrate carries a thin transparent film consisting-of magnesium difluoride, silicon monoxide or silicon dioxide, and a thin aluminium film formed on said thin transparent film for reflecting light incident thereto through the liquid crystal cell.
- chrome has been vapor-deposited on a rear surface of a glass substrate to form a reflection film. Reflectivity of light of the conventional reflection mirror with the chrome film, however, could be increased at most to about 50% even if the chrome film is thick enough.
- the reflection mirror using the liquid crystal cell used as a dazzle-free interior room mirror of an automotive vehicle, for instance, is manufactured in general in a series of processes shown in Fig. 7.
- soda glass is cut in a shape of transparent glass substrate.
- a transparent conductive film is formed on the glass substrate as an electrode.
- the transparent conductive films use indium tin oxides in which weight percentage ratio between In 2 0 3 and S.102 is 95:5 and are formed to film thickness of 1000 A by an electron beam under 350°C-400°C and oxygen partial pressure of 1 x 1 0-2 Pa-5x 10- 2 Pa.
- acid- resistant resist ink is printed on the transparent conductive film over a whole range corresponding to a dazzle-free portion so that a masking is provided.
- the substrate with the transparent conductive film is dipped for two minutes under temperature of 45°C in a fluid solution mixture of concentrated hydrochloric acid and water in 1:1 ratio so that surrounding portions of the transparent conductive film corresponding to a sealing portion is removed therefrom.
- the resist ink is removed by the use of organic solvent, trichloroethylene.
- orientating processing is done to orient the liquid crystal parallelly.
- polyimide solution is slushed by a spinner at 3500 rpm and thereafter the substrate is maintained at temperatures of 300°C for 30 minutes and 400°C for 30 minutes and fired thereby to form an orientation film on the conductive film.
- rubbing the orientation film is done by the use of chemical fiber cloth to provide orientation of liquid crystal filled in later.
- sealing material is printed on side portions by the use of epoxy resin.
- glass fiber particles in particle diameter of 10 11m are spread as spacers on the orientation film.
- a pair of glass substrates each being processed as above described are put one upon another in parallel and maintained under temperature of 100°C for 2 hours for bonding so that a liquid crystal cell is provided.
- a reflection film is vapor-deposited on the other end surface of one of the transparent glass substrates to form a mirror surface thereat.
- liquid crystal is filled in an inner space of the liquid crystal cell by a decompressed injection process.
- an injection opening is sealed with epoxy adhesive.
- forming the mirror surface is done after the orientating process. This is for the reason that, if forming the mirror surface is done before the orientating process, the mirror surface formed beforehand might be hurt in later processes such as the orientating process, it might be hurt when the glass substrate is attached to holding jigs for the orientating processing, for instance, and the mirror surface might become uneven. Therefore, forming the mirror surface must be done the orientating process.
- Fig. 1 is a cross-sectional view showing the structure of the dazzle-free reflection mirror according to the first embodiment of the present invention.
- the reflection mirror primarily comprises an attachment 1 for attaching the reflection mirror to a vehicle ceiling (not shown), a light- shielding frame body 2 supported by the attachment 1, a pair of glass substrates 3a and 3b, a liquid crystal cell 50 sandwiched between the glass substrates 3a and 3b for controlling the transmittivity of light, a semitransparent or half mirror 8, a photo diode 10 for detecting the intensity of light incident thereto and a driving circuit 9 supported within the frame body 2 for driving the liquid crystal cell 50 in accordance with the detected intensity of light.
- the liquid crystal cell 50 and the semitransparent mirror 8 could be manufactured in a conventional method shown in Fig. 7.
- the photo diode 10 is provided behind the semi-transparent mirror 8 as a photo sensor for detecting the light having passed through the liquid crystal cell 50 and the semitransparent mirror 8.
- the photo diode 10 is supported on a substrate 91 supporting the driving circuit 9 thereon.
- the driving circuit 9 is supplied with the electric power from a battery mounted on the automotive vehicle through power supply cables 92.
- the liquid crystal cell 50 sandwiched between the glass substrates 3a and 3b has, as seen from the light incident side or front side, a transparent electrode layer 4a consisting of ITO (Indium Tin Oxide), an orientation film 5a for orientating liquid crystal parallelly, a liquid crystal layer 6 consisting of the nematic liquid crystal for generating DSM (Dynamic Scattering Mode), an orientation film 5b and a transparent electrode layer 4b.
- the liquid crystal cell 50 is structured to generate dynamic scattering upon an application of an electric voltage across the electrodes 4a and 4b and control the transmittivity of light incident from the glass substrate 3a therethrough so that the total reflectivity of light of the whole reflection mirror is electrically controlled.
- the thickness of the transparent electrode layers 4a and 4b was set to 100 nm whereas the thickness of the liquid crystal layer 6 was set to 10 j-tm.
- the half mirror 8 which is manufactured at the step 118 has a first transparent thin film layer 8a formed on the rear side surface of the glass substrate 3b, a thin semitransparent reflection layer 8b and a second transparent thin film layer 8c.
- the first thin film layer 8a was formed by vapor-depositing magnesium difluoride (MgF 2 ) to the thickness of 130 nm by the electron beam under substrate temperature of 150°C.
- the semi- transparent reflection layer 8b was formed by vapor-depositing aluminum to the thickness of 350 A under substrate temperature of 150°C.
- the second thin film layer 8c was formed by vapor-depositing magnesium difluoride (MgF 2 ) to the thickness of 70 nm under substrate temperature of 150°C.
- the semitransparent mirror 8 manufactured in the above-described manner had 55% in reflectivity of light and 8% in transmittivity of light. This transmittivity of light is higher by 8 times than the transmittivity 1 % of chrome.
- the adhesiveness of aluminum to the glass substrate 3b is increased and, since the surface thereof is protected by the second thin film layer 8c, it is prevented from peeling off and being hurt.
- Fig. 2 is a graph showing a relation between the voltage applied to the liquid crystal cell 50 and the transmittivity of light measured by detecting the light having passed through the semitransparent mirror 8 in the dazzle-free reflection mirror according to the first embodiment.
- the transmittivity of light of the liquid crystal is at the maximum value and the rate of light passing through the semi- transparent mirror 8 is at about 8%, when no voltage is applied. It will be also understood that, with the voltage of about 20 volts, the transmittivity of light is decreased to 4% because of the dynamic scattering effect which changes the transmittivity of light passing through the semitransparent mirror 8.
- the first thin film layer 8a and the semitransparent reflection layer 8b were varied in the first embodiment.
- the result of the experiment is shown in Fig. 5 in which the reflectivity of light of the reflection mirror is plotted with respect to the thickness of the semitransparent reflection layer 8b with the thickness of the first thin film layer 8a as a parameter.
- the thickness of the first thin film layer 8a had no substantial influence on the reflectivity of light. This means that the reflectivity of light is substa- nially dependent only on the thickness of the semitransparent reflection layer 8b.
- magnesium difluoride (MgF 2 ) used forthefirst and second thin film layers 8a and 8c was replaced by silicon dioxide (Si0 2 ), silicon monoxide (SiO) or titanium dioxide (TiO z ).
- Fig. 3 is an electric wiring diagram showing the driving circuit 9 used in the first embodiment.
- the intensity of light detected by the photo diode 10 differs in dependence on whether dazzling of light is prevented or not
- the intensity of light detected at the time of preventing dazzling of light becomes lower than that detected at the time of not preventing dazzling of light and, therefore, it is necessary to change a switching point of the driving circuit for driving the liquid crystal cell 50.
- an inverting input terminal of a comparator 18 is connected to receive, as a detection voltage, a voltage V1 at a connection between a resistor 12 and the photo diode 10.
- a non-inverting input terminal of the comparator 18 is connected to receive, as a reference voltage, a voltage V2 produced by dividing the battery voltage Vcc by a resistor 13 and a resistor 14.
- a positive feedback resistor 17 is connected between the non-inverting input terminal and an outputterminal of the comparator 18. The positive feedback resistor 17 is used, as is known well with respect to the operation of comparators, to provide a hysteresis characteristic so that the switching point thereof is changed.
- the output terminal of the comparator 18 is connected to an exclusive-OR circuit 19 and an output terminal of the latter is connected to the transparent electrode 4a of the liquid crystal cell 50.
- an output terminal of a pulse oscillator 200 is applied to the exclusive-OR circuit 19.
- the output terminal of the pulse oscillator 200 is connected also to the transparent electrode 4b of the liquid crystal cell 50.
- the pulse oscillator 200 comprise C-MOS inverters 23, 24 and 25, resistors 20 and 21 and a capacitor 22 which determine an oscillation frequency.
- the reference voltage V2 of the comparator 18 is set at the low and high voltages Vt2 and Vt1 in response to the low and high levels of an output voltage V3 of the comparator 18, respectively.
- the voltage V1 responsively decreases as shown in (b) of Fig. 4 and reaches the reference voltage Vt2 at a time t1.
- the output voltage V3 of the comparator 18 becomes high at the time t1.
- the reference voltage V2 is set at Vt1.
- the pulse oscillator 200 produces, as shown in (d) of Fig. 4, an output voltage V4 in a rectangular waveform at a fixed frequency. Accordingly the voltages V5 and V4 applied to the electrodes 4a and 4b of the liquid crystal cell 50 are in an opposite phase relation to each other by means of the exclusive-OR circuit 19 only when the voltage V3 is at the high level, and the voltage applied across the liquid crystal cell 50 changes as shown in (e) of Fig. 4.
- the time t2 indicates the time when the voltage V1 produced by the photo diode 10 reaches the reference voltage Vt1 due to decrease in the intensity of light incident to the reflection mirror, that is, the time when the dazzle-free mode is terminated.
- FIG. 6 A second embodiment of the reflection mirror is shown in Fig. 6, in which same reference numerals are used to designate the same or similar parts as in the first embodiment shown in Fig. 1.
- a pair of liquid crystal cells 50 and 50' are stacked to each other to form a guest/host liquid crystal cell and the semitransparent mirror 8 is formed on the rear side surface of the glass substrate 3b of the liquid crystal cell 50' in the same manner as in the first embodiment shown in Fig. 1.
- capability of vapor-depositing aluminum is increased and prevention of peeling off is enabled by virtue of the first thin film layer. Further, by virtue of a second thin film layer, hurting an aluminum film surface is prevented.
- the sensitivity in detecting a dazzle-free condition is increased and the reflection image in the dazzle-free condition becomes more clear with the semi- transparent mirror layer being used for the dazzle-free reflection mirror.
Description
- The invention relates to a controllable reflection mirror according to the preamble of
claim 1. - US-A-3,862,798 discloses a rear view mirror assembly comprising a reflective surface, and a liquid crystal assembly covering the reflective surface. The liquid crystal assembly comprises a thin layer of liquid nematic material sandwiched between rigid panes of transparent material, the rigid panes having a thin, transparent coating of conductive material thereon in uniform contact with the nematic material. The controlled output of a voltage source is applied to the coatings of conductive material so that transmittivity of light by the nematic material is changed.
- DE-A-2,653,818 discloses a liquid crystal cell comprising a glass substrate for changing transmittivity of light incident thereto in accordance with an electric voltage applied thereto. The glass substrate carries a thin transparent film consisting-of magnesium difluoride, silicon monoxide or silicon dioxide, and a thin aluminium film formed on said thin transparent film for reflecting light incident thereto through the liquid crystal cell.
- In a conventional reflection mirror, chrome has been vapor-deposited on a rear surface of a glass substrate to form a reflection film. Reflectivity of light of the conventional reflection mirror with the chrome film, however, could be increased at most to about 50% even if the chrome film is thick enough.
- It has been suggested to increase the reflectivity of light to as high as 80%-90%, for instance, by the use of aluminum. It was disadvantageous, however, that aluminum film peels off because of insufficient adhesiveness thereof to the glass substrate when aluminum is vapor-deposited directly on the glass substrate.
- To overcome the disadvantage, it has been suggested in the Janpanese publication, "Journal of Applied Physics, vol. 29, No. 3, page 141", that chromel be used between the glass substrate and the aluminum film to improve adhesiveness of the aluminum film to the glass substrate.
- It was still disadvantageous, however, in the following points. (1) Total reflectivity of light cannot be increased sufficiently high even if the aluminum film is formed on the chromel film, since reflectivity and transmitivity of light of chromel is low as chrome is. (2) Chromel cannot be vapor-deposited on a liquid crystal cell since, when chromel is vapor-deposited on a rear surface of the glass substrate used to support the liquid crystal cell in which there are a pair of transparent electrodes, a pair of orientation films and a liquid crystal, the orientation of the orientation films is disturbed by the temperature at the vapor-depositing.
- The second disadvantage (2) is explained hereinunder in more detail. The reflection mirror using the liquid crystal cell used as a dazzle-free interior room mirror of an automotive vehicle, for instance, is manufactured in general in a series of processes shown in Fig. 7.
- Firstly, at a
step 100, soda glass is cut in a shape of transparent glass substrate. At astep 102, a transparent conductive film is formed on the glass substrate as an electrode. The transparent conductive films use indium tin oxides in which weight percentage ratio between In203 and S.102 is 95:5 and are formed to film thickness of 1000 A by an electron beam under 350°C-400°C and oxygen partial pressure of 1 x 1 0-2 Pa-5x 10-2 Pa. Next, at astep 104, acid- resistant resist ink is printed on the transparent conductive film over a whole range corresponding to a dazzle-free portion so that a masking is provided. At astep 106 thereafter, the substrate with the transparent conductive film is dipped for two minutes under temperature of 45°C in a fluid solution mixture of concentrated hydrochloric acid and water in 1:1 ratio so that surrounding portions of the transparent conductive film corresponding to a sealing portion is removed therefrom. At astep 108, the resist ink is removed by the use of organic solvent, trichloroethylene. Then, at astep 110, orientating processing is done to orient the liquid crystal parallelly. In the orientating processing, polyimide solution is slushed by a spinner at 3500 rpm and thereafter the substrate is maintained at temperatures of 300°C for 30 minutes and 400°C for 30 minutes and fired thereby to form an orientation film on the conductive film. Then rubbing the orientation film is done by the use of chemical fiber cloth to provide orientation of liquid crystal filled in later. At astep 112, sealing material is printed on side portions by the use of epoxy resin. Further, at astep 114, glass fiber particles in particle diameter of 10 11m are spread as spacers on the orientation film. At astep 116, a pair of glass substrates each being processed as above described are put one upon another in parallel and maintained under temperature of 100°C for 2 hours for bonding so that a liquid crystal cell is provided. At astep 118, a reflection film is vapor-deposited on the other end surface of one of the transparent glass substrates to form a mirror surface thereat. At astep 120, liquid crystal is filled in an inner space of the liquid crystal cell by a decompressed injection process. At astep 122, an injection opening is sealed with epoxy adhesive. - As described above, forming the mirror surface is done after the orientating process. This is for the reason that, if forming the mirror surface is done before the orientating process, the mirror surface formed beforehand might be hurt in later processes such as the orientating process, it might be hurt when the glass substrate is attached to holding jigs for the orientating processing, for instance, and the mirror surface might become uneven. Therefore, forming the mirror surface must be done the orientating process.
- Here, it has been found experimentally that, when the liquid crystal cell obtained after the orientating process is heated to above 160°C, the orientation is disturbed. This means that temperature of the substrate must be maintained below 160°C at least in the process of forming the mirror surface. In the case of forming the mirror surface of metals such as chrome, chromel or aluminum by vapor-depositing in a vacuum, however, it is generally considered to heat the substrate to temperature as high as 200°C-300°C so that adhesiveness of the metal film to the substrate is increased. Therefore, the abovedescribed metals cannot be used for forming the mirror surface in the case of the relfection mirror using the liquid crystal cell in which the mirror surface must be formed below temperature of 160°C.
- It is the object of the invention to provide a controllable reflection mirror according to the preamble of
claim 1 in such a way that the transparent film and the aluminum film allow to have an undamaged reflector and an undamaged liquid crystal orienting layer on the same substrate. - This object is achieved by the features in the characterizing part of
claim 1. - Embodiments of the invention are described in more detail in connection with the attached drawings.
- Fig. 1 is a cross-sectional view showing a reflection mirror according to a first embodiment of the present invention;
- Fig. 2 is a graph showing a relation between a voltage applied to a liquid crystal cell and a transmittivity of light having passed reflection mirror according to the first embodiment;
- Fig. 3 is a circuit diagram showing a driving circuit for the reflection mirror according to the first embodiment;
- Fig. 4 is a timing chart showing waveforms of signals produced in the driving circuit shown in Fig. 3;
- Fig. 5 is a graph showing relations between thickness of aluminum film and reflectivity of light of the reflection mirror according to the first embodiment;
- Fig. 6 is a cross-sectional view showing partly a reflection mirror according to a second embodiment of the present invention; and
- Fig. 7 is a flow chart showing a series of prior art processing steps for manufacturing the reflection mirror.
- Fig. 1 is a cross-sectional view showing the structure of the dazzle-free reflection mirror according to the first embodiment of the present invention. The reflection mirror primarily comprises an
attachment 1 for attaching the reflection mirror to a vehicle ceiling (not shown), a light-shielding frame body 2 supported by theattachment 1, a pair ofglass substrates liquid crystal cell 50 sandwiched between theglass substrates half mirror 8, aphoto diode 10 for detecting the intensity of light incident thereto and adriving circuit 9 supported within theframe body 2 for driving theliquid crystal cell 50 in accordance with the detected intensity of light. It should be noted here that theliquid crystal cell 50 and thesemitransparent mirror 8 could be manufactured in a conventional method shown in Fig. 7. - The
photo diode 10 is provided behind thesemi-transparent mirror 8 as a photo sensor for detecting the light having passed through theliquid crystal cell 50 and thesemitransparent mirror 8. Thephoto diode 10 is supported on a substrate 91 supporting thedriving circuit 9 thereon. Thedriving circuit 9 is supplied with the electric power from a battery mounted on the automotive vehicle through power supply cables 92. - The
liquid crystal cell 50 sandwiched between theglass substrates transparent electrode layer 4a consisting of ITO (Indium Tin Oxide), anorientation film 5a for orientating liquid crystal parallelly, aliquid crystal layer 6 consisting of the nematic liquid crystal for generating DSM (Dynamic Scattering Mode), anorientation film 5b and atransparent electrode layer 4b. Theliquid crystal cell 50 is structured to generate dynamic scattering upon an application of an electric voltage across theelectrodes glass substrate 3a therethrough so that the total reflectivity of light of the whole reflection mirror is electrically controlled. The thickness of thetransparent electrode layers liquid crystal layer 6 was set to 10 j-tm. - The
half mirror 8 which is manufactured at thestep 118 has a first transparentthin film layer 8a formed on the rear side surface of theglass substrate 3b, a thinsemitransparent reflection layer 8b and a second transparentthin film layer 8c. The firstthin film layer 8a was formed by vapor-depositing magnesium difluoride (MgF2) to the thickness of 130 nm by the electron beam under substrate temperature of 150°C. The semi-transparent reflection layer 8b was formed by vapor-depositing aluminum to the thickness of 350 A under substrate temperature of 150°C. The secondthin film layer 8c was formed by vapor-depositing magnesium difluoride (MgF2) to the thickness of 70 nm under substrate temperature of 150°C. Thesemitransparent mirror 8 manufactured in the above-described manner had 55% in reflectivity of light and 8% in transmittivity of light. This transmittivity of light is higher by 8 times than thetransmittivity 1 % of chrome. The adhesiveness of aluminum to theglass substrate 3b is increased and, since the surface thereof is protected by the secondthin film layer 8c, it is prevented from peeling off and being hurt. - Fig. 2 is a graph showing a relation between the voltage applied to the
liquid crystal cell 50 and the transmittivity of light measured by detecting the light having passed through thesemitransparent mirror 8 in the dazzle-free reflection mirror according to the first embodiment. As will be understood from the graph, the transmittivity of light of the liquid crystal is at the maximum value and the rate of light passing through the semi-transparent mirror 8 is at about 8%, when no voltage is applied. It will be also understood that, with the voltage of about 20 volts, the transmittivity of light is decreased to 4% because of the dynamic scattering effect which changes the transmittivity of light passing through thesemitransparent mirror 8. - To evaluate influence of the thickness of the first
thin film layer 8a on the reflectivity of light, the firstthin film layer 8a and thesemitransparent reflection layer 8b were varied in the first embodiment. The result of the experiment is shown in Fig. 5 in which the reflectivity of light of the reflection mirror is plotted with respect to the thickness of thesemitransparent reflection layer 8b with the thickness of the firstthin film layer 8a as a parameter. As will be understood from Fig. 5, the thickness of the firstthin film layer 8a had no substantial influence on the reflectivity of light. This means that the reflectivity of light is substa- nially dependent only on the thickness of thesemitransparent reflection layer 8b. - It was also confirmed that substantially the same result as in the abovedescribed first embodiment could be obtained when magnesium difluoride (MgF2) used forthefirst and second thin film layers 8a and 8c was replaced by silicon dioxide (Si02), silicon monoxide (SiO) or titanium dioxide (TiOz).
- Fig. 3 is an electric wiring diagram showing the driving
circuit 9 used in the first embodiment. In view of the fact that the intensity of light detected by thephoto diode 10 differs in dependence on whether dazzling of light is prevented or not, the intensity of light detected at the time of preventing dazzling of light becomes lower than that detected at the time of not preventing dazzling of light and, therefore, it is necessary to change a switching point of the driving circuit for driving theliquid crystal cell 50. - As shown in Fig. 3, an inverting input terminal of a
comparator 18 is connected to receive, as a detection voltage, a voltage V1 at a connection between aresistor 12 and thephoto diode 10. A non-inverting input terminal of thecomparator 18 is connected to receive, as a reference voltage, a voltage V2 produced by dividing the battery voltage Vcc by aresistor 13 and aresistor 14. On the other hand, apositive feedback resistor 17 is connected between the non-inverting input terminal and an outputterminal of thecomparator 18. Thepositive feedback resistor 17 is used, as is known well with respect to the operation of comparators, to provide a hysteresis characteristic so that the switching point thereof is changed. The output terminal of thecomparator 18 is connected to an exclusive-OR circuit 19 and an output terminal of the latter is connected to thetransparent electrode 4a of theliquid crystal cell 50. On the other hand, an output terminal of apulse oscillator 200 is applied to the exclusive-OR circuit 19. The output terminal of thepulse oscillator 200 is connected also to thetransparent electrode 4b of theliquid crystal cell 50. Thepulse oscillator 200 comprise C-MOS inverters resistors capacitor 22 which determine an oscillation frequency. - Operation of the driving
circuit 9 shown in Fig. 3 is described with reference to a timing chart of Fig. 4. The reference voltage V2 of thecomparator 18 is set at the low and high voltages Vt2 and Vt1 in response to the low and high levels of an output voltage V3 of thecomparator 18, respectively. When the intensity of the light incident to thephoto diode 10 increases gradually as shown in (a) of Fig. 4, the voltage V1 responsively decreases as shown in (b) of Fig. 4 and reaches the reference voltage Vt2 at a time t1. Then, as shown in (c) of Fig. 4, the output voltage V3 of thecomparator 18 becomes high at the time t1. With this high level voltage V3, the reference voltage V2 is set at Vt1. Dynamic scattering is generated with the alternating current voltage being applied to theliquid crystal cell 50 as decribed later and, as a result, the intensity of the incident light detected bythephoto diode 10 decreases by an amount A as shown in (a) of Fig. 4. Therefore, although the voltage V1 increases correspondingly, but it does not reach the reference voltage Vt1. Thus, the output voltage V3 of thecomparator 18 is maintained high until the time t2. - The
pulse oscillator 200 produces, as shown in (d) of Fig. 4, an output voltage V4 in a rectangular waveform at a fixed frequency. Accordingly the voltages V5 and V4 applied to theelectrodes liquid crystal cell 50 are in an opposite phase relation to each other by means of the exclusive-OR circuit 19 only when the voltage V3 is at the high level, and the voltage applied across theliquid crystal cell 50 changes as shown in (e) of Fig. 4. This meansthatthe liquid crystal cell is driven into the dazzle-free mode during the time period tl-t2 by the alternating current votlage. The time t2 indicates the time when the voltage V1 produced by thephoto diode 10 reaches the reference voltage Vt1 due to decrease in the intensity of light incident to the reflection mirror, that is, the time when the dazzle-free mode is terminated. - A second embodiment of the reflection mirror is shown in Fig. 6, in which same reference numerals are used to designate the same or similar parts as in the first embodiment shown in Fig. 1.
- In the second embodimentshown in Fig. 6, a pair of
liquid crystal cells 50 and 50' are stacked to each other to form a guest/host liquid crystal cell and thesemitransparent mirror 8 is formed on the rear side surface of theglass substrate 3b of the liquid crystal cell 50' in the same manner as in the first embodiment shown in Fig. 1. - According to the present invention described hereinabove, capability of vapor-depositing aluminum is increased and prevention of peeling off is enabled by virtue of the first thin film layer. Further, by virtue of a second thin film layer, hurting an aluminum film surface is prevented. The sensitivity in detecting a dazzle-free condition is increased and the reflection image in the dazzle-free condition becomes more clear with the semi- transparent mirror layer being used for the dazzle-free reflection mirror.
Claims (7)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP35827/84 | 1984-02-27 | ||
JP59035827A JPS60178402A (en) | 1984-02-27 | 1984-02-27 | Half mirror |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0154861A1 EP0154861A1 (en) | 1985-09-18 |
EP0154861B1 true EP0154861B1 (en) | 1988-06-01 |
Family
ID=12452785
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP85101928A Expired EP0154861B1 (en) | 1984-02-27 | 1985-02-22 | Reflection mirror |
Country Status (4)
Country | Link |
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US (1) | US4655549A (en) |
EP (1) | EP0154861B1 (en) |
JP (1) | JPS60178402A (en) |
DE (1) | DE3563124D1 (en) |
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US5122647A (en) * | 1990-08-10 | 1992-06-16 | Donnelly Corporation | Vehicular mirror system with remotely actuated continuously variable reflectance mirrors |
US5148014A (en) * | 1990-08-10 | 1992-09-15 | Donnelly Corporation | Mirror system with remotely actuated continuously variable reflectant mirrors |
US5446576A (en) * | 1990-11-26 | 1995-08-29 | Donnelly Corporation | Electrochromic mirror for vehicles with illumination and heating control |
FR2686164B1 (en) * | 1992-01-13 | 1995-05-05 | Corning Inc | DEVICE FOR AUTOMATICALLY CONTROLLING THE REFLECTANCE OF A MIRROR. |
US5168378A (en) * | 1992-02-10 | 1992-12-01 | Reliant Laser Corporation | Mirror with dazzle light attenuation zone |
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-
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-
1985
- 1985-02-22 US US06/704,401 patent/US4655549A/en not_active Expired - Fee Related
- 1985-02-22 DE DE8585101928T patent/DE3563124D1/en not_active Expired
- 1985-02-22 EP EP85101928A patent/EP0154861B1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
US4655549A (en) | 1987-04-07 |
DE3563124D1 (en) | 1988-07-07 |
EP0154861A1 (en) | 1985-09-18 |
JPS60178402A (en) | 1985-09-12 |
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